Screening And Identification Of A Strain Producing Antifungal Substance

Plant diseases cause decreased crop yields, lower quality. Food production has huge losses because of plant diseasesevery year. Plant diseases caused by fungal is the worst disease of three diseases. Its harm was more serious than bacterial diseases and viral diseases. Method of biological control of plant diseases is considered to be an effective way. Because agricultural antibiotics have advantages of low toxicity, high selectivity, short time left and non-pollution. Agricultural antibiotics as an important group of biological pesticides are more and more attention. Screening a highly activity strain producing antifungal substance was studied in this paper. The fermentation conditions and fermentation products of the strain also were studied. The results will provide reference for further finding and developing the new, efficient and natural non-toxic biological pesticides.Screening model of screening of a strain producing antifungal substance was established by Sclerotinia sclerotiorum and Botrytis cinerea as the indicator bacteria. Strain al was got after primary screening and rescreening. It has high activity of inhibiting Sclerotinia sclerotiorum and Botrytis cinerea.The morphological, physiological and biochemical characteristics and16S rDNA of strain al were identified. The results showed that strain al was Bacillus subtilis.Single factor experiment with response surface method was uesd to find the optimal control conditions of strain al. The optimal control conditions:substrate:lactose28.2g, yeast extract,28.4g, sodium chloride5g, water1L, pH9. Fermentation conditions:rotational speed150rpm, inoculum concentration12%, fermentation temperature28.43℃, fermentation time24.51h, volume of medium50mL, the inoculation time24h.Physical and chemical properties on strain al producing antifungal substance were studied in this work. The results showed that antifungal substance was acid-resistant, and it can keep activity at neutral condition and light irradiation. But it was not stable at alkaline condition and ultraviolet irradiation. It had a low antifungal activity when temperature above100℃. The results of extraction experiment study showed that antifungal substance was acidic and water-soluble substance.